Literature is available in many different formats today. Two popular formats for books are audio books and electronic books (e-Books). An audio book is typically a recording of commercially printed material, such as a published book or journal. An e-book, also known as a digital book, includes text that forms a digital media equivalent of a conventional printed book, sometimes restricted with a digital rights management system. Electronic book content may be read on devices such as e-Readers, personal computers, notebooks, netbooks, desktops, tablets, slates, personal digital assistants, cell phones, and etcetera.